ivor and olive lewis on tue 8 may 12
Dear James Freeman,
Accepting your examples of the things that can happen when Oxidised Iron
(Steel objects) are combined with clay and a glaze batch, there is still
nothing which tells me that oxidised iron has the nature of a flux.
As I recall, in the process of welding wrought iron by forging two section
of metal together, silver sand, that is finely divided quartz, is used as a
"flux" to remove "Mill Scale" which is expelled from the joint to solidify
as Slag.
My first edition of Hamer's Dictionary has several pages devoted to Iron
Oxides. His description of Black Iron oxide does not suggest fluxing
activity, either as a molten solvent, as a viscosity modifier or to alter
surface tension, but rather some form of chemical reaction.
Quoting F. Hamer on black iron oxide, "It is stable at room temperature but
becomes excited at red heat. This excitement is a loosening of the molecula=
r
bonds thereby allowing the black iron oxide to combine with silicates..."
Page 164, Iron Oxide: Black Iron Oxide. Sounds like a chemical reaction to
me. Your student's glaze behaved as a solvent for the oxidised iron or stee=
l
and in solution increased glaze fluidity. If you wish, diminished its
viscosity.
Best regards,
Ivor Lewis,
REDHILL,
South Australia
Robert Harris on tue 8 may 12
In reply to both James and Ivor - I wonder Ivor, if when you looked up
"Black Iron Oxide", it was referring to the stuff we commonly buy
(Fe3O4, a.k.a Iron (II,III) Oxide) as black Iron oxide, rather than
FeO.
It seems to me that your example of silver sand implies that the
combination of Iron Oxide and Quartz does indeed have a melting point
below that of either of them. Whether the Iron is fluxing the quartz,
or vice versa, seems irrelevant to me.
I have a very nice "floating green" glaze, (boron phase separation)
with some black iron oxide (N.B. Fe3O4 not FeO!) in it, which runs a
bit too much. I have been trying to reduce the flux without
eliminating the phase separation, without much luck. As a result of
the earlier conversation I had already decided to replace the black
iron oxide with red iron oxide to see if this reduces the fluxing
activity appreciably. Since I fire to Cone 9 (i.e. well after the
transition point of Fe2O3 to FeO), it may well be that it will still
run.
Incidentally I have never been able to find any actual scientific
reports that Fe2O3 becomes FeO at 2250F which is the commonly quoted
temperature. Does anyone know you actually came up with this number?
Like James, I will let you know of my results.
Robert
On Tue, May 8, 2012 at 7:29 AM, James Freeman
wrote:
> On Tue, May 8, 2012 at 1:13 AM, ivor and olive lewis
> wrote:
>
> Accepting your examples of the things that can happen when Oxidised Iron
> (Steel objects) are combined with clay and a glaze batch, there is still
> nothing which tells me that oxidised iron has the nature of a flux.
>
>
>
>
> Hi, Ivor...
>
> As I said earlier, I am not a chemist at all. =3DA0In the spirit of your =
ol=3D
d
> ClayArt friend, I could google a bunch of stuff for you and pretend I
> understand it, but I'll leave that to you. =3DA0A google search on the te=
rm
> "FeO flux" will give you a bunch of references that are fairly easy to
> understand for non-chemists such as myself. =3DA0Searching the same term =
on
> google scholar will give you tons of serious scientific stuff like your
> friend used to quote.
>
> The Hamer reference I provided says that FeO is a powerful flux, as does
> Digital Fire. =3DA0There was also a non-scientific paper on google
> demonstrating that an iron-bearing clay remained porous when fired in a
> neutral atmosphere, but became vitreous when fired in reduction, and
> remained vitreous even when re-fired back to a bright orange state in an
> electric kiln (seemingly confirming John H's idea that reduced iron oxide
> that is locked inside a vitreous melt will be essentially unreachable by
> atmospheric oxygen).
>
> I will offer only this additional bit, from Edouard's scientist friend:
>
> "In a stoneware clay, the transformation of ferric oxide to ferrous oxide
> by reduction above 1200=3DB0C involves the formation of iron silicate or
> fayalite FeSiO4 (2FeO + SiO2), whose clay fluxing eutectic is rather brut=
=3D
al
> if the initial content in Fe2O3 is high. FeO thus acts like a fast-acting
> flux for silica. If the reduction penetrates deeply into the clay
> containing Fe2O3 in great amounts, it is likely to create
> deformations.Without the reduction effect, ferric oxide Fe2O3 does not
> react directly
> with silica." I have, cooling in my electric kiln right now, three
> different tests of the five flavors of iron oxide I had in stock. =3DA0I'=
ll
> report back if I find any interesting results.
>
> All the best.
> ...James
>
> James Freeman
>
> "Talk sense to a fool, and he calls you foolish."
> -Euripides
>
> http://www.jamesfreemanstudio.com
> http://www.flickr.com/photos/jamesfreemanstudio/
> http://www.jamesfreemanstudio.com/resources
--=3D20
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James Freeman on tue 8 may 12
On Tue, May 8, 2012 at 1:13 AM, ivor and olive lewis
wrote:
Accepting your examples of the things that can happen when Oxidised Iron
(Steel objects) are combined with clay and a glaze batch, there is still
nothing which tells me that oxidised iron has the nature of a flux.
Hi, Ivor...
As I said earlier, I am not a chemist at all. In the spirit of your old
ClayArt friend, I could google a bunch of stuff for you and pretend I
understand it, but I'll leave that to you. A google search on the term
"FeO flux" will give you a bunch of references that are fairly easy to
understand for non-chemists such as myself. Searching the same term on
google scholar will give you tons of serious scientific stuff like your
friend used to quote.
The Hamer reference I provided says that FeO is a powerful flux, as does
Digital Fire. There was also a non-scientific paper on google
demonstrating that an iron-bearing clay remained porous when fired in a
neutral atmosphere, but became vitreous when fired in reduction, and
remained vitreous even when re-fired back to a bright orange state in an
electric kiln (seemingly confirming John H's idea that reduced iron oxide
that is locked inside a vitreous melt will be essentially unreachable by
atmospheric oxygen).
I will offer only this additional bit, from Edouard's scientist friend:
"In a stoneware clay, the transformation of ferric oxide to ferrous oxide
by reduction above 1200=3DB0C involves the formation of iron silicate or
fayalite FeSiO4 (2FeO + SiO2), whose clay fluxing eutectic is rather brutal
if the initial content in Fe2O3 is high. FeO thus acts like a fast-acting
flux for silica. If the reduction penetrates deeply into the clay
containing Fe2O3 in great amounts, it is likely to create
deformations.Without the reduction effect, ferric oxide Fe2O3 does not
react directly
with silica." I have, cooling in my electric kiln right now, three
different tests of the five flavors of iron oxide I had in stock. I'll
report back if I find any interesting results.
All the best.
...James
James Freeman
"Talk sense to a fool, and he calls you foolish."
-Euripides
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/resources
Rimas VisGirda on wed 9 may 12
I built a bust into which I stuck about 100-200 6 inch common (iron) =3D
=3D0A=3D0AI built a bust into which I stuck about 100-200 6 inch common (ir=
on) =3D
finishing nails. It bisqued to 05 just fine then went into a cone 10 reduct=
=3D
ion fire. Neither the head nor the nails had any glaze on them. On opening =
=3D
the kiln there were pointed (sharp) residue barely protruding from the head=
=3D
and a pile of black nails around the base. The sharp residue appeared as y=
=3D
ou would take a tube of silicone and squeeze out a blob then pull up leavin=
=3D
g a form that looks something like a Hershey's kiss... The nails at the bas=
=3D
e were not melted and had a thick layer of black that I, at the time, thoug=
=3D
ht might be something like slag -having done some gas as well as=3DA0 arc w=
el=3D
ding, I was familiar with slag... I suppose after reading parts of this thr=
=3D
ead the coating could have been black iron oxide... I don't intend to enter=
=3D
the discussion, I just throw in my experience for you who may be intereste=
=3D
d to interpret my empirical observation...=3D0A=3D0A=3D0AAgain I include a =
jpeg f=3D
or James and/or Mel to post on their site for those that are interested in =
=3D
the visual. -Rimas=3D0A=3D0AIvor writes:=3D0AAccepting your examples of the=
thing=3D
s that can happen when Oxidised Iron=3D0A(Steel objects) are combined with =
cl=3D
ay and a glaze batch, there is still=3D0Anothing which tells me that oxidis=
ed=3D
iron has the nature of a flux.
James Freeman on wed 9 may 12
On Wed, May 9, 2012 at 1:08 PM, Rimas VisGirda wrote:
I built a bust into which I stuck about 100-200 6 inch common (iron)
finishing nails. It bisqued to 05 just fine then went into a cone 10
reduction fire.
The photo of Rimas' self-portrait bust (nails fired at cone 10 R) is up on
my Flickr page (http://www.flickr.com/photos/jamesfreemanstudio/). I have
also posted a very poorly shot photo of a very old piece of mine, which
contains nails (carpet tacks, actually) fired at cone 04 in an electric
kiln. I chipped off a layer of oxide (of some kind), revealing the
basically intact nails. Note that the nails had no effect on the fired
glaze, which remained very stiff. Contrast this with what happened to
Rimas' nails in reduction (and higher temperature, and likely more time).
Had his piece been glazed, the nails would have likely taken most of the
glaze with them on their trip to the kiln shelf.
Interesting stuff!
...James
James Freeman
"Talk sense to a fool, and he calls you foolish."
-Euripides
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/resources
ivor and olive lewis on thu 10 may 12
Dear Robert Harris,
In response to your question I suppose the answer has to be "Yes"
since Wustite, with a formula of FeO is unstable and reverts to metallic
iron and magnetite.
Iron oxide combines with Silica to generate Fayalite (on cooling from the
melt) which has a melting point of 1205 deg C (2201 deg F)
Relating to your "Floating Green". You are concerned about Viscosity. The
anecdotal evidence from Mel Jacobson and others is that Iron Oxides diminis=
h
viscosity and increase fluidity. Rather than change your flavour of Iron
oxide I would suggest adding a small proportion of Aluminium oxide, either
as clay or as Alumina hydrate. Do a line blend and test on sloping/vertical
test pieces.
The interactions of Silica and Iron oxides are summarised on Fe-Si-O, fig 8=
2
from "Phase Diagrams for Ceramists". This not only gives temperatures (C)
but also the partial pressures of Oxygen.
Best regards,
Ivor Lewis,
REDHILL,
South Australia
Robert Harris on thu 10 may 12
Thanks Ivor - with regards to the floating green. Since it is a boron
phase separation green, I cannot add alumina as this loses the "boron
blue" background.
I have done line blends with clay, silica, custer and whiting. Either
I lose the green, or it still runs.
Hence my last gasp idea of changing the iron.
Robert
On Thu, May 10, 2012 at 3:44 AM, ivor and olive lewis
wrote:
> Dear Robert Harris,
>
> In response to your question I suppose the answer has to be "Yes"
>
> since Wustite, with a formula of FeO is unstable and reverts to metallic
> iron and magnetite.
>
> Iron oxide combines with Silica to generate Fayalite (on cooling from the
> melt) which has a melting point of 1205 deg C (2201 deg F)
>
> Relating to your "Floating Green". You are concerned about Viscosity. The
> anecdotal evidence from Mel Jacobson and others is that Iron Oxides dimin=
ish
> viscosity and increase fluidity. Rather than change your flavour of Iron
> oxide I would suggest adding a small proportion of Aluminium oxide, eithe=
r
> as clay or as Alumina hydrate. Do a line blend and test on sloping/vertic=
al
> test pieces.
>
> The interactions of Silica and Iron oxides are summarised on Fe-Si-O, fig=
82
> from "Phase Diagrams for Ceramists". This not only gives temperatures (C)
> but also the partial pressures of Oxygen.
>
>
> Best regards,
>
> Ivor Lewis,
> REDHILL,
> South Australia
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